Fatal error for plugin install

I get the following error whenever I try to install a plugin. If I try to upload the folder myself via FTP, it simply doesn’t show up in my plugin menu.
Fatal error: Cannot redeclare class pclzip in /home/content/a/d/i/adijaffe/html/wordpress/wp-admin/includes/class-pclzip.php on line 171

Hi there, I would check your directory structure, your plugins should be here, \wordpress\wp-content\plugins, I would also chck where you have upladed the snap shots plugin, dlete it and upload it to the plugins folder.
hope you get there.
mike.

They’re all in the right folder, I found the problem with snapshots, it was the code in the footer. But I still can’t add any plugins. Is there a maximum limit of plugins? If not, is there a way to rebuild some index file that would make it reexamine the plugins in the folder?